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Power Inverter Online Diagnostics
Knobloch, Jan ; Chlebiš,, Petr (referee) ; Drábek,, Pavel (referee) ; Klíma, Bohumil (advisor)
This doctoral thesis focuses on the problems of IGBT failure prediction in pulse converters using measurable changes of selected parameters (so--called trending variables) being influenced of transistor degradation during aging. Firstly the state--of--the--art in this field is presented in the dizertation. The description of designed and constructed automated measurement stand follows, enabling monitoring and recording of switching processes during accelerated aging. Further the problems of high--bandwidth measurement of electrical quantities during IGBT switching are described. Especially the problems of current sensing are analyzed and the most suitable sensor is selected. The data recorded using the developed apparatus served to identify potential trending variables allowing the failure prediction. Here the dependence of trending variables on aging and on parasitic influences (current, temperature, voltage) had to be distinguished. Finally the evaluation of trending variables is performed. Their insignificant sensitivity on accelerated aging is shown which complicates their practical implementation for the purpose of failure prediction.
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Analysis of the appropriateness of the data from the IMU / GNSS units
Holouš, Karel ; Hanuš, Jan
The object of the air campaign Analysis of the IMU/GNSS data and it’s suitability, was to create a sufficient amount of GPS data to analyze the appropriateness of using the IMU/GNSS data for comparison with other IMU/GNSS data recorded at the same time by the ordering client. Based on the initial request data were acquired using the installed GPS sensors, on-board navigation system GARMIN G1000 and GNSS Applanix POS/AV 410. Data acquisition was performed during a single flight in total duration of 0:58 on February 16, 2016. During this flight we performed complete set of predetermined tests during different flight regimes.\n\n
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Investigation of droplet nucleation in CCS relevant systems – Design and testing of a CO2 branch of the mixture preparation device.
Vinš, Václav ; Čenský, Miroslav ; Hykl, Jiří ; Hrubý, Jan
A unique in-house designed experimental apparatus for investigation of nucleation of droplets in CCS relevant systems is being developed by our team. The nucleation is measured with the help of a rapid pressure drop within an expansion chamber. In this study, a CO2 branch representing an important part of the mixture preparation device (MPD) was designed, assembled and tested. MPD is intended for preparation of CO2-rich mixtures in a sense of accurate setting of flow rates of individual gaseous components through the experimental section with the expansion chamber. In the CO2 branch, the saturated liquid CO2 is pressurized by a supercritical pump to the pressures of up to 340 bar. The required mass flow of the supercritical CO2 is accurately tuned with a help of a set of stainless steel capillary tubes. Needed lengths of the capillary tubes were determined with a help of a one-dimensional numerical model allowing prediction of both isothermal and adiabatic flow conditions.
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Energy sensitive X-ray radiography for the non-destructive inspection of historical paintings
Žemlička, J. ; Jakoubek, J. ; Kroupa, M. ; Hradil, David ; Hradilová, J. ; Mislerová, H.
Pigments containing iron, although they form a very large group, have never been considered very suitable for datation of color layers and identification of the origin of the painting, due to their abundant occurrence in nature, good availability and widespread use in all historical and pre-historical periods of time. In this paper we have verified that mineralogical composition of clay minerals in earthy pigments is a suitable tool for more detailed specification of material provenance and, in the case of ground layers, also the provenance of the artwork as such. It was obviously convenient to preferably use raw materials from a close and thus also cheaper source. For the purposes of statistical comparison we evaluated elemental composition of earthy grounds on 70 paintings from the 16(th)-18(th) centuries from Czech collections. We performed detailed mineralogical analyses for a selected representative number of grounds on 35 samples in total. We discerned 6 types of material in total 2 types of boles, 3 types of other earths, and one type representing iron-rich red from oxidized zones of hydrothermal ore deposits. We were able to distinguish between earthy pigments of Central European origin (coming from Czech and Bavarian locations) and those coming from North-Italian sources. Thus we were able to assign anonymous paintings to an appropriate place of origin.
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Voltage sensitive fluorescent protein based on the motor protein prestin
DIVOKÝ, Karel
The aim of this work was to create a series of fluorescently labeled constructs based on the motor protein prestin, express these constructs in mammalian cells, and measure their linear dichroism by two photon polarization microscopy, in order to develop a genetically encoded optical probe of cell membrane voltage. This thesis provides an introduction to current methods of observing electrical activity in neurons, describes the method of two-photon polarization microscopy, describes our results in preparing the abovementioned constructs, and summarizes our microscopic observations.
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Využití ukazatele EVA při hodnocení výkonnosti podniků ve vybraném odvětví
Palínková, Iveta
The main goal of this thesis is to propose appropriate recommendations towards maintaining or improving financial performance of selected companies in the logistics industry. At the beginning of the practical part is characterized the transport industry and storage. Further presents three selected companies. For all from these companies is monitored 2009 - 2012. For complex view of the current state of performance of companies is worked out traditional financial analysis and calculated economic value added. Then is worked out analyse of sensitivity and factor analysis, which identifies the factors influencing the level of EVA. The thesis is finished by an evaluation of the results, comparing between companies and propose recommendations for maintaining or improving financial performance.
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Films of Metal Nanoparticles Deposited on Semiconductors by Electrophoresis: Technology and Characterization
Žďánský, Karel ; Zavadil, Jiří ; Kacerovský, Pavel ; Kostka, František ; Lorinčík, Jan ; Černohorský, O. ; Fojtík, A. ; Müller, M. ; Kostejn, M.
Layers of nanoparticles in micelle enclosures were deposited on InP substrates by electrophoresis from isooctane colloid solutions containing Pd or Ag nanoparticles. The layers were investigated by SIMS, low-temperature photoluminescence spectroscopy and topography, absorption spectroscopy, Raman spectroscopy and sensitivity to hydrogen. Photoluminescence of InP was enhanced by the layers of Pd or Ag nanoparticles. Schottky barriers made on the n-type InP with layers containing Pd nanoparticles showed significant sensitivity to hydrogen in contrast to those containing Ag nanoparticles.
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The Transitional Regime of Backward-Facing Step Flows
Tihon, Jaroslav ; Pěnkavová, Věra ; Havlica, Jaromír ; Šimčík, Miroslav
The backward-facing step flow is investigated experimentally (electrodiffusion technique) and numerically (CFD software Fluent) at moderate Reynolds numbers achieved in a water channel. The direction sensitive sensors are used to measure the wall shear rate behind the step and detect the near-wall extent of different flow-recirculation regions. 2D numerical simulations provide additional information on the global flow rearrangement caused by the change of operational parameters (channel expansion ratios, inlet flow conditions). At the transitional flow regime, the near-wall flow exhibits an unsteady character with a high sensitivity to external low-frequency perturbations (intrinsic flow instability). The inlet pulsatile forcing is found to affect strongly the overall flow structure behind the step, resulting in the reattachment length reduction and the reverse flow intensification.
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